1. Field of the Invention
The present invention generally relates to an organic electroluminescent (to be abbreviated as “EL” hereinafter) device and a method for manufacturing the same and, more particularly, to an organic EL device with efficient heat dissipation employing an additional heat dissipation layer and a method.
2. Description of the Prior Art
The organic EL device has attracted tremendous attention due to its advantages over other display panels. These advantages include larger visual angle, shorter response time, smaller dimension in thickness, lower power consumption, simpler fabrication, no need for backlighting, and the ability for light emitting in a full color range.
Please refer to FIG. 1, which is a cross-sectional view showing the structure of a conventional organic EL device in accordance with the prior art. The organic EL device is characterized in that at least a first electrode 12 is formed on a substrate 11. On the first electrode 12, there is an organic layer 13 comprising at least an organic emitting layer, and a second electrode 14 formed by evaporation in turn. Then, a sealing cap layer 15 formed of resin is employed to protect the organic layer 13 from the external oxygen or the moisture.
Since, in an organic EL device, the light is generated when the electrons and holes from the first electrode 12 and second electrode 14 combine in the organic layer 13 to excite the organic emitting layer, it is inevitable that heat is generated during the luminescence process. Once the heat encounters the moisture existing inside the sealing cap layer 15, dark spots due to oxidation will be formed on the surface of the organic layer 13. The existence of such dark spots adversely affects the luminescence quality such as luminescence intensity and luminescence uniformity of an organic EL device. According to the so-called “10-degree rule”, the lifetime of the device reduces to half for every 10-degree rise in operation temperature. Therefore, for a highly heat-generating device, the performance as well as the lifetime depends strongly on the ability in heat dissipation. More seriously, the lifetime of an organic EL device may be substantially shortened.
In order to overcome the image defects and shortened lifetime due to the disability in heat dissipation, the industry has developed a number of prior art organic EL displays, for example, in U.S. Pat. No. 5,948,552 “Heat-resistant organic electroluminescent device” filed by Antoniadis, et al. and U.S. Pat. No. 4,895,734 “Process for forming insulating film used in thin film electroluminescent device” filed by Yoshida, et al. However, in the aforementioned prior arts, additional materials are required with little concerns in structural reform. Little improvement in device performance is disclosed for organic EL devices.
Therefore, there is need in providing an organic EL device with efficient heat dissipation employing an additional heat dissipation layer and a method for manufacturing such a device so as to prolong the lifetime and improve the reliability.